Characterized by a lack of empathy and increased antisocial and risk-taking behavior, psychopathy is a personality disorder that afflicts less than one percent of the general population. However, among adult offenders, psychopathy afflicts approximately 10 to 25 percent of adult offenders .
Recent research suggests that psychopaths have core fear-processing defects, which means that they lack the ability to feel fear, which may be due to dysregulation of the limbic system. Comprised of multiple smaller structures located in the middle and lower end of the brain, this system is known to play an important role in fear experience and has thus unsurprisingly been associated with psychopathy causation. To explore this further, Vasileia Karasavva’s review paper, The Fear Factor: Fear Defects in Psychopathy as an Index of Limbic Dysregulation, discusses the current literature on the neurobiological underpinning of psychopathy.
When asked to recall instances of fear, psychopathic individuals report experiencing fear less frequently than non-psychopathic controls . However, studying the fear response of psychopathic individuals in a lab setting has revealed even more interesting results. Taking a Pavlovian conditioning approach by pairing a pain signal with an electrical shock administered to themselves or others, it has been shown that psychopathic individuals exhibit lower levels of fear compared to non-psychopathics. This study  supports the idea that psychopathic individuals experience depleted feelings of fear.
In addition, the psychopathic individuals had a reduced activation of the autonomic nervous system activation (ANS), measured by an increased heart rate, skin conductance and blink reflex response. ANS is responsible for the fight or flight response and activated in response to fear; its dysregulation therefore may explain blunted fear response in psychopathic individuals.
Researchers now have developed a way to look at specific brain regions of psychopathic individuals to monitor dysregulation at subsections. For example, magnetic resonance imaging (MRI) was used to show that psychopathic brains have fewer nerve cells in the limbic system and surrounding regions2. In addition, increased morphological and connectivity defects were also observed in psychopathic individuals compared to controls. Karasavva suggests that these defects affect the brain functionality of psychopathic individuals. Indeed, functional MRI has shown that brains of psychopathic individuals are functionally transmit fewer signals compared to non-psychopathic individuals.
Bringing the current literature together, Karasavva’s review article research highlights that psychopathologic symptoms have a biological basis rooted in structural and functional alternations of the limbic system. This serves as an important cornerstone to guide future research into the cellular mechanistic unpinning’s of psychopathy. Karasavva highlights that these findings can drive drug development that aim to repairing the issues, for example by inducing nerve cell proliferation and resorting limbic system morphology. Karasavva suggests that this research opens the door to some of the remaining questions regarding the origins of psychopathy-associated symptoms. For example, are they present at birth or do they emerge later due to environmental influences? Answers to these questions, Karasavva believes, will likely play an important role in the complete understanding of the neurobiology of psychopathy.
Serin, R., Forth, A., Brown, S., Nunes, K., Bennell, C., & Pozzulo, J. (2011). Psychology of criminal behaviour: A Canadian perspective, Second Canadian Edition. Pearson Toronto.
Karasavva, V. (2019). The Fear Factor: Fear Deficits in Psychopathy as an Index of Limbic Dysregulation. Journal of Young Investigators. 36 (6).